1. Field of the Invention
The present invention relates to a process for the preparation of 4-hydroxyphenyl benzoate derivatives.
2. The Prior Art
4-Hydroxyphenyl benzoate derivatives are important organic intermediates which have hitherto been difficult to prepare. For example, 4-hydroxyphenyl benzoate derivatives in which a radical having an alkenyl or alkynyl group is located in the 1-position of the benzoic acid ring are used for the preparation of liquid-crystalline siloxane-containing side-chain polymers.
The main problem associated with the synthesis of 4-hydroxyphenyl benzoate derivatives consists in coupling bifunctional hydroquinone derivative with benzoic acid compounds on only one side. In the preparative process known from U.S. Pat. No. 5,211,877, allyloxybenzoyl chloride is reacted with a very large excess of hydroquinone. The disadvantage of this method is that the excess hydroquinone has to be laboriously separated off after the reaction, leading to a poor space-time yield of 4-hydroxyphenyl allyloxybenzoate.